1. Field of the Invention
The present invention relates to a new and improved method for the adjustment of an optical row of sensors.
In its more particular aspects, the invention relates to a method for the adjustment or compensation of an optical row of sensors which, for the purpose of guiding a self-propelled or driverless vehicle along an optical guideway or track, is attached at the vehicle in a direction substantially transverse to the direction of vehicle travel. The scanning operation as far as the number of sensors is concerned is accomplished with a timewise delay, and the measurement signals are evaluated by means of a subsequently connected computer serve to control a steering mechanism.
2. Description of Background and Other Information
The use of optical sensors for guiding a self-propelled or driverless vehicle, and which optical sensors scan an optical guideway or guide track or strip applied to a floor or base surface, has been found to be exceedingly advantageous. This is particularly the case because the mounting of a guideway or track upon the floor or base surface can be accomplished without any great problems and there is not required any post-treatment of such floor or base surface as would be otherwise required when laying a metallic guide wire. Hence, such type of installation can be installed without any problems in already existing buildings or structures which are equipped with traveling vehicles.
In U.S. Pat. No. 4,703,240, granted Oct. 27, 1987, there is disclosed such a scanning apparatus, wherein a row of optical sensors scan a guide track mounted at a floor. The thus obtained signals are weighted based upon a threshold value, and thus, the position of the guide track or strip is determined based upon the distribution of the signals as viewed over the width of the sensor arrangement. If the guide track or strip is arranged off-center, then there is controlled a vehicle steering mechanism. In order to compensate different tolerances of the individual sensors, there is proposed that the determined measurement values of neighboring or plural sensors are compared with one another in order to thus obtain a smoothed measurement value curve. As a result, it is indeed possible to compensate in part tolerances, but on the other hand, this smoothing operation leads to inaccuracies, particularly at the region between the interface of the floor and the guide strip and thus to deviations in maintaining travel along the guide track.
A further optical sensor apparatus is known to the art from U.S. Pat. No. 4,775,023, granted Oct. 4, 1988. In this arrangement, and viewed over the row of sensors, each second sensor is alternatingly controlled or powered such that the transmitted light cones do not intersect and are not able to mutually disturb one another. The evaluation of the signals likewise is correlated to a predetermined threshold value and results in a binary value 0 or 1 corresponding to the signal. These binary values are weighted to an average or mean value and cause the generation of an appropriate control signal for a steering apparatus. There is not contemplated an adjustment or tuning of the sensors with respect to one another, with the result that the existence of spurious or faulty signals due to the presence of markedly drifting sensors is possible.
However, in actual practice, it has been found that maintaining an exact travel track or path, particularly at the delivery and receiving locations for the vehicles, is necessary and there must be ensured maintaining of the travel path over the guideway or strips.
It is therefore necessary that the measurement signals generated by the sensors are solely dependent upon the scanning operation and specifically the position of the guide track or strip and that further influences, such as for example component tolerances of the sensors, do not influence the measurement signals.
Also, with the aforementioned state of the art, there is not contemplated any post-regulation of the optical scanning system upon impairment of the light reflection from the floor and the guide strips.
However, such is necessary, particularly when the system is in operation over longer periods of time without supervision.